The Potential Impact of Nanofluid Enhancements on the Performance of Heat Exchangers

The potential benefit of using nanofluids in heat-exchanger applications is explored using an epsilon-NTU analysis. As expected, the enhancement in number of transfer units (NTU) is largest when the convection resistance associated with the flow to be enhanced is a large contributor to the overall thermal resistance of the baseline heat exchanger. Likewise, as expected, nanofluid enhancement has a larger impact for poorly performing baseline heat exchangers. For a single-pass cross-flow configuration, with both fluids unmixed, the ratio of heat capacity rates is unimportant in nanofluid enhancement. Among all flow arrangements investigated, the concentric-tube, counterflow arrangement shows highest improvement in heat duty for a prescribed convective heat-transfer enhancement. The enhancement in convection also suggests a significant saving of heat-transfer area/material, and the saving also increases with the resistance ratio of the enhanced stream to the overall thermal resistance. The impact of specific heat reduction due to the existence of nanoparticles in the stream is also investigated.